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Purpose: The purpose of this study is to reveal the usability of waste paper sludge on the production of composite materials and the printability of their surfaces were investigated. Design/methodology/approach: First, composite plates were produced by using dried and milled waste sludge together with polyester resin and epoxy. Screen printing using water, solvent and UV-based inks were carried out. Findings: It was determined that UV and solvent-based inks in both resin groups were permanently attached to the surface of composite plates produced using paper mill waste sludge, while it was found that the adhesion was not achieved sufficiently in cardboard factory waste sludge. Originality/value: The unique aspect of this study is obtained the composite plates from paper mill and cardboard mill waste sludge and improved the printability of them. [ABSTRACT FROM AUTHOR]

Surface decorated wood-based panels with melamine formaldehyde resin (MF) impregnated paper is highly favored by consumers due to its outstanding appearance and durable performance. However, the laminated composites would encounter hygroscopic expansion and damage that affect its service and aesthetics in long-term humid environments. This study aims to construct highly durable superhydrophobic surface to address this issue. Firstly, a controlled micro rough structure on stainless steel plates which were built with sandblasting was successfully duplicated onto the surface of MF impregnated paper laminated medium density fiberboard (MDF) using the embossing method. Following that, a spray treatment with hydrophobic nanoparticles was employed to the laminated composite surface, ultimately resulting in a superhydrophobic coating with a contact angle up to 163°. To confirm the durability of the fabricated superhydrophobic layer, linear abrasion test, water droplet impact test, sand impact test, and tape peeling test were carried out. The results demonstrated that even after severe processed conditions, the contact angle of the decorated surface remained above 150°. And the decorated laminate successfully passed both self-cleaning and dirt resistance challenge, clearly indicating the outstanding durability of superhydrophobic structure. Furthermore, water absorption thickness expansion measurement was done to verify the dimensional stability of the laminate in humid conditions. This research presented a straightforward and cost-effective approach to fabricate highly durable superhydrophobic MF impregnated paper decorated laminates, offering a dependable strategy for research and applications in related domains. [ABSTRACT FROM AUTHOR]

The article presents the discussion on Insight's current awareness service covering British and international publications, conference proceedings, and multimedia products.

With the high precision requirements and the trend of large-scale composite parts, the development of composite molds is imminent. The short carbon fiber (SCF) composite mold is mainly prepared by the technological process flow of composite sheet injection, the bonding of composite plates, and machining. However, the current process optimization method has not matured adequately, and there are still many shortcomings, for example, low precision and high cost. In this paper, the optimization method of SCF/polyetherimide (PEI) composite molds is proposed. Many experiments have been conducted, and the results show that the coefficient of thermal expansion of composite samples can be effectively reduced and the mechanical properties can be improved by optimizing the SCF weight ratio and carbon fiber length. The bonding strength of composite joints in a high-temperature environment can be improved by optimizing the bonding process parameters and modification by carbon nanotubes. Based on the above optimization method, the SCF/PEI composite mold is prepared, and the C-shaped beam composite part is fabricated by using this mold. Compared with the part made by aluminum mold, the shape accuracy of the C-shaped beam composite part is proven high through digital measurement technology. [ABSTRACT FROM AUTHOR]

Delamination represents one of the most significant and dangerous damages in composite plates. Recently, many papers have presented the capability of structural health monitoring (SHM) techniques for the investigation of structural delamination with various shapes and thickness depths. However, few studies have been conducted regarding the utilization of convolutional neural network (CNN) methods for automating the non-destructive testing (NDT) techniques database to identify the delamination size and depth. In this paper, an automated system qualified for distinguishing between pristine and damaged structures and classifying three classes of delamination with various depths is presented. This system includes a proposed CNN model and the Lamb wave technique. In this work, a unidirectional composite plate with three samples of delamination inserted at different depths was prepared for numerical and experimental investigations. In the numerical part, the guided wave propagation and interaction with three samples of delamination were studied to observe how the delamination depth can affect the scattered and trapped waves over the delamination region. This numerical study was validated experimentally using an efficient ultrasonic guided waves technique. This technique involved piezoelectric wafer active sensors (PWASs) and a scanning laser Doppler vibrometer (SLDV). Both numerical and experimental studies demonstrate that the delamination depth has a direct effect on the trapped waves' energy and distribution. Three different datasets were collected from the numerical and experimental studies, involving the numerical wavefield image dataset, experimental wavefield image dataset, and experimental wavenumber spectrum image dataset. These three datasets were used independently with the proposed CNN model to develop a system that can automatically classify four classes (pristine class and three different delamination classes). The results of all three datasets show the capability of the proposed CNN model for predicting the delamination depth with high accuracy. The proposed CNN model results of the three different datasets were validated using the GoogLeNet CNN. The results of both methods show an excellent agreement. The results proved the capability of the wavefield image and wavenumber spectrum datasets to be used as input data to the CNN for the detection of delamination depth. [ABSTRACT FROM AUTHOR]

The mode manipulation of Lamb waves plays an important role in damage detection and identification of damage types, location, and size. In this paper, we propose a composite phononic crystal (PC) plate with antisymmetric and symmetric PCs for realizing mode conversion from A0 to S0 mode of Lamb waves. The theoretical analysis, numerical simulations, and experimental validation are introduced and the mode conversion mechanism of the composite PC plate is systematically investigated. The effect of geometrical parameters on band structures of antisymmetric and symmetric PCs is first discussed. Then multi-physics field simulation models are developed and in-plane displacement fields are obtained in numerical simulations, which shows that the mode conversion is enhanced when the period number of the antisymmetric PC decreases and that of symmetric the PC increases. The composite PC plate specimens are fabricated with precision wire cutting technology for experimental measurements and the self-designed polyvinylidene fluoride (PVDF) comb transducer is used to stimulate the Lamb waves. The experimental results are consistent with the numerical simulations, which demonstrate that the proposed composite PC plate can achieve the mode conversion from A0 to S0 mode of Lamb waves. Our proposed structures have applicable values for the mode manipulation of Lamb waves in damage detection. [ABSTRACT FROM AUTHOR]

In view of the increasingly prominent noise problem, more and more attention has been paid to the research of sound insulation materials and structures. This paper takes aluminum foam laminated structural plate as the research object. The numerical model of sound insulation was derived using equivalent parameter method, and the sound insulation performance of aluminum foam composite structural plate was tested using a standing wave tube. The experimental results show that the transfer loss of aluminum foam composite structure with 5 mm and 10 mm core layer thickness is increased by 10 dB and 17 dB on average compared with ordinary base aluminum plate. The calculated results of transfer loss in effective range are in good agreement with the experimental results. The error is only 2–5 dB at low frequencies. At the high-frequency stage, although the error increases slightly, the overall trend of the two changes is consistent. The degree of coincidence increases with the increase of frequency. It provides an important theoretical basis for the research direction of sound insulation theoretical model of aluminum foam laminated structure, and also lays a foundation for the optimization of subsequent mathematical model. [ABSTRACT FROM AUTHOR]

Composite laminates have become increasingly popular in industries like aerospace and shipbuilding. In practical applications, the creation of notches in composite laminates is often necessary to enable assembly and modifications. This rise in the use of notched composite laminates highlights the need for reliable methods to predict potential failures in these components. With these predictions, the safety and reliability of composite structures can be ensured by preventing catastrophic failures. The present paper investigates the use of the Virtual Isotropic Material Concept (VIMC) combined with the Finite Fracture Mechanics (FFM) criterion to predict the Last Ply Failure (LPF) load in keyhole notched composite laminates and under mode I loading conditions. Experimental tests were conducted to measure the LPF load of E-glass/Epoxy keyhole notched specimens, and the results were compared with the predicted results using the VIMC-FFM criterion. The paper also derives an expression for the Stress Intensity Factor (SIF) function for a crack that emanates from the keyhole notch tip under mode I loading conditions. The derived equation matches very well with numerical data and have a mean absolute error about 2% in the studied domain. The study shows that the VIMC-FFM criterion predicts the LPF load of keyhole notched composite laminates with acceptable accuracy and in a simple and low-cost manner. [ABSTRACT FROM AUTHOR]

This paper provides a brief review on modeling of composite structures. Composite structures in this paper refer to any structure featuring anisotropy and heterogeneity, including but not limited to their traditional meaning of composite laminates made of unidirectional fiber-reinforced composites. Common methods used in modeling of composite structures, including the axiomatic method, the formal asymptotic method, and the variational asymptotic method, are illustrated in deriving the classical lamination theory for the composite laminated plates. Future research directions for modeling composite structures are also pointed out. [ABSTRACT FROM AUTHOR]

New three-phase composite structures reinforced synergistically by nano-fillers and macroscopic fibers have great application potential. This paper presents a general framework for material properties calculation and the free vibration analysis of three-phase composite shell structures. Based on this methodological system, the free vibration characteristics of three types of nano-enhanced functionally graded three-phase composite cylindrical shells are investigated. First, the equivalent mechanical properties of these three three-phase composites were evaluated using the Halpin–Tsai and Mori–Tanaka models. The governing equations for the cylindrical shells were derived based on the first-order shear deformation theory (FSDT) and Hamilton's principle. The equations were discretized using Galerkin's method and solved to obtain the natural frequencies and mode shapes. The finite element simulation results and existing literature verified the accuracy and reliability of the method in this paper. The synergistic effects of nano-reinforced fillers and macroscopic fibers on the free vibrations of these structures were also analyzed. Among them, the natural frequency of the three-phase composite cylindrical shells was the highest when graphene platelets (GPLs) were used as the nano-reinforced fillers, which was 150.32% higher than that of fiber-reinforced epoxy composite cylindrical shells. These studies provide theoretical guidance for the design and manufacture of such symmetric or antisymmetric structures in the future. [ABSTRACT FROM AUTHOR]

Four different composite coupling beam-to-composite plate shear wall (CPSW/CF) connection details were developed and proposed. Six large-scale specimens representing the four connections were designed, fabricated, and tested. The connections were subassemblies of coupled composite plate shear walls/concrete filled (CC-PSW/CF) subjected to cyclic lateral loading. The coupling beams were designed to be flexure-critical with clear span-to-depth (Lb/d) ratios of 3.5 or 5.1. This paper presents the experimental program, capacities, and detailed behavioral observations of all six specimens. The effects of connection type and Lb/d ratio on the ultimate strength, stiffness, ductility, and failure modes are evaluated. Major limit states and events included yielding of the steel plates comprising the coupling beam, followed by local inelastic buckling, fracture initiation in the base metal (near the weld toes), and fracture propagation through the beam flange and web plates, leading to loss of flexural strength and failure. All the connections were able to develop and transfer the flexural capacity of the composite beam section. The composite coupling beams developed flexural capacities (10%–50%) greater than those calculated using the plastic stress distribution method. The underlying reasons for this overstrength are evaluated. The AISC flexural stiffness equation for filled composite sections could reasonably estimate the stiffness of the composite coupling beam sections. A fiber-based model of the cross-section was used to calculate the section moment–curvature response of the filled composite beam sections. The calculated flexural capacities were consistent with those calculated by the plastic stress distribution method but lower than the experimentally observed values. The flexural stiffness values were slightly higher than the experimental results. For more accurate comparisons with experimental results, a numerical model is needed to estimate the cyclic lateral load-deformation response while accounting for the effects of local buckling, low cycle fatigue, and fracture. [ABSTRACT FROM AUTHOR]

In the present work, the general stiffness matrix method is extended in the case of a functionally graded magneto-electro-elastic plate to analyze the free vibration response of a functionally graded composite plate. The material properties are assumed to be continuously graded in the thickness direction. The novelty of this paper is to utilize this efficient method to the dynamic analysis of a wide range of composite (multilayer) plates, with linear or non-linear thickness profiles, and functionally graded in the thickness, without any limitation. The convergence of this method is thoroughly discussed. Here, the converged results are obtained when the number of sub-layer is $ N \le 11 $ N ≤ 11. A parametric study was also conducted to show the effect of gradation of mechanical properties of the composite on the phase velocity and the modal shape. The dynamic model developed here can be used in the graded material design of the functionally graded piezoelectric-piezomagnetic (noted FGPPM) composite plate for achieving specified dynamic characteristics. [ABSTRACT FROM AUTHOR]

This paper outlines an experimental investigation into the durability of large-scale adhesively bonded joints with a thick layer of methyl methacrylate adhesive (MMA). Ageing has been performed by immersion in a 3.5 wt% NaCl solution for 10 weeks at 50°C. Two aged and one unaged specimen were subjected to tensile testing, and three aged and one unaged specimen were loaded up to ~ 3.5 million fatigue cycles followed by a residual tensile test. The ductility of the adhesive is affected by ageing and fatigue testing. Despite a decrease in ductility, the plastic zone development was adequate for the required strain redistribution without compromising the joint performance (strength and stiffness) demonstrating the fatigue tolerance of the joint. The shear, longitudinal, and peel strain values in the adhesive bulk are evaluated by digital image correlation. The shear strength values are significantly higher than the requirements following from the design. All specimens failed by sudden delamination of the composite plate. Post-mortem analysis showed no corrosion travel at the interface of steel and adhesive. [ABSTRACT FROM AUTHOR]

It is widely recognized that certain structures, when subjected to static compression, may exhibit a bifurcation point, leading to the potential occurrence of a secondary equilibrium path. Also, there is a tendency of deflection increment without a bifurcation point to occur for imperfect structures. In this paper, some relatively unknown phenomena are investigated. First, it is demonstrated that in some conditions, the linear buckling mode shape may differ from the result of geometrically nonlinear analysis. Second, a mode jumping phenomenon is described as a transition from a secondary equilibrium path to an obscure one as a tertiary equilibrium path or a second bifurcation point. In this regard, some non-square plates with unsymmetric layer arrangements (in the presence of extension–bending coupling) are subjected to a uniaxial in-plane compression. By considering the geometrically linear and nonlinear problems, the bucking modes and post-buckling behaviors, e.g., the out-of-plane displacement of the plate versus the load, are obtained by ANSYS 2023 R1 software. Through a parametric analysis, the possibility of these phenomena is investigated in detail. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of non-homogeneous elastic foundations on the free vibration characteristics of functionally graded graphene platelets reinforced composite plates submerged in fluid medium. A novel aspect of this study lies in exploring various distributions of the foundation, positioned either centrally within the plates or along their edges. The stiffness of the foundation is computed using Selvadurai's method, which accounts for subgrade soil properties and foundation depth. Material properties of the plates are examined by employing the rule of mixtures alongside the Halpin–Tsai micromechanical model. Hydrostatic pressure and free surface waves are not considered, given the assumption of an ideal and incompressible fluid. The theoretical framework is grounded in a novel inverse trigonometric shear deformation plate theory, where the transverse shear stress distribution is established using a newly developed inverse trigonometric function. The equations of motion are efficiently resolved through Galerkin's method. The efficacy of this approach lies in its utilization of integration to address the distribution issue of the foundation, obviating the need for deploying intricate algorithms. The proposed theory demonstrates enhanced accuracy in predicting natural frequencies compared to other published shear deformation plate theories. Moreover, this paper delves into the effect of material properties and the fluid environment on the natural frequencies of the structures. Particularly significant is our thorough investigation of the impact of variations in the locations, material properties, and sizes of the foundation on the free vibration of these plates, all of which bear great importance in structural design. [ABSTRACT FROM AUTHOR]

The advantages of carbon nanotubes (CNTs) in fortifying the glass fiber reinforced polymeric (GFRP) composites are discussed in this paper. Bolted steel straps are utilized at the edges of composite plate to establish clamped conditions in the test setup. To minimize uncertainties caused by bolt attachments, a genetic algorithm-based model updating approach has been implemented by introducing artificial linear springs at the margins to achieve a better balance between theory and reality. The accuracy of the plate's results (natural frequencies and mode shapes) is verified, and the mechanical properties of randomly dispersed CNTs are incorporated in the formulations of folded plates. Remarkably, the motion equations are brought forward by the first order shear deformation theory (FSDT). Thereafter, two-directional generalized differential quadrature (2D-GDQ) technique is employed to determine natural frequencies from available motion, continuity, and boundary equations. The results of the folded plate are validated first by an experimental modal testing and finally some effective parameters such as folding angle, CNT weight ratio, boundary condition and flange-shape length are examined. [ABSTRACT FROM AUTHOR]

The abalone shell, a composite material whose cross-section is composed of inorganic and organic layers, has high strength and toughness. Inspired by the abalone shell, several multi-layer composite plates with different layer sequences and thicknesses are studied as bullet-proof material in this paper. To investigate the ballistic performance of this multi-layer structure, the complete characterization model and related material parameters of large deformation, failure and fracture ofAl2O3 ceramics andCarbon Fiber Reinforced Polymer (CFRP) are studied. Then, 3D finite element models of the proposed composite plates with different layer sequences and thicknesses impacted by a 12.7 mm armor-piercing incendiary (API) are built using Abaqus to predict failure. The simulation results show that the CFRP/Al2O3 ceramic/Ultrahigh Molecular Weight Polyethylene (UHMWPE)/CFRP (1 mm/4 mm/4 mm/1 mm) composite is the optimized stack of layers. The simulation results under specified layer sequence and thickness have a reasonable correlation with the experimental results and reflect the failure and fracture of the multi-layer composite protective armor. [ABSTRACT FROM AUTHOR]

The nonlinear static and vibration response of micro composite sandwich plate with honeycomb core have been investigated in this paper. The displacement–strain of skins via higher-order shear deformation theory (HSDT) is obtained. In frame work Halpin–Tsai model the composites plate with two layers of Graphene platelet reinforcement (GPLRC) with uniform distribution pattern and a hexagonal honeycomb core is considered. The governing equations of sandwich plate are derived by implementing Hamilton's principle and solved Perturbation method. For investigating the accuracy, this paper is validated with other previous researches and a good correlation is observed between the results. Finally, the important findings of this research indicate that the ratio of core thickness, inclined angle, and thickness to inclined length have significant effects on nonlinear frequencies–amplitude and deflection response. Based on the results of this article designers can development of different parts of aircraft. [ABSTRACT FROM AUTHOR]

The lattice metamaterial has attracted extensive attention due to its excellent specific strength, energy absorption capacity, and strong designability of the cell structure. This paper aims to explore the functional nickel plating on the basis of biomimetic-designed lattice structures, in order to achieve higher stiffness, strength, and energy absorption characteristics. Two typical structures, the body-centered cubic (BCC) lattice and the bioinspired hierarchical circular lattice (HCirC), were considered. The BCC and HCirC lattice templates were prepared based on DLP (digital light processing) 3D printing. Based on this, chemical plating, as well as the composite plating of chemical plating followed by electroplating, was carried out to prepare the corresponding nickel-plated lattice structures. The mechanical properties and deformation failure mechanisms of the resin-based lattice, chemically plated lattice, and composite electroplated lattice structures were studied by using compression experiments. The results show that the metal coating can significantly improve the mechanical properties and energy absorption capacity of microlattices. For example, for the HCirC structure with the loading direction along the x-axis, the specific strength, specific stiffness, and specific energy absorption after composite electroplating increased by 546.9%, 120.7%, and 2113.8%, respectively. The shell–core structure formed through composite electroplating is the main factor for improving the mechanical properties of the lattice metamaterial. In addition, the functional nickel plating based on biomimetic structure design can further enhance the improvement space of mechanical performance. The research in this paper provides insights for exploring lighter and stronger lattice metamaterials and their multifunctional applications. [ABSTRACT FROM AUTHOR]

Composite materials are widely used, but they are often subjected to impacts from foreign objects, causing structural damage. To ensure the safety of use, it is necessary to locate the impact point. This paper investigates impact sensing and localization technology for composite plates and proposes a method of acoustic source localization for CFRP composite plates based on wave velocity-direction function fitting. This method divides the grid of composite plates, constructs the theoretical time difference matrix of the grid points, and compares it with the actual time difference to form an error matching matrix to localize the impact source. In this paper, finite element simulation combined with a lead-break experiment is used to explore the wave velocity-angle function relationship of Lamb waves in composite materials. The simulation experiment is used to verify the feasibility of the localization method, and the lead-break experimental system is built to locate the actual impact source. The results show that the acoustic emission time-difference approximation method can effectively solve the problem of impact source localization in composite structures, and the average localization error is 1.44 cm and the maximum localization error is 3.35 cm in 49 experimental points with good stability and accuracy. [ABSTRACT FROM AUTHOR]

A large number of experiments show that composite materials usually show different modulus properties in tension and compression (bi-modulus). However, for actual composite engineering structures, especially complex models, the numerical simulation calculation is usually based on a single modulus. In order to consider the different modulus characteristics of composite materials in tension and compression, researchers put forward simplified constitutive models of dual-modulus materials. However, these constitutive models have not been verified by a large number of experiments, especially by complex models. In this paper, the GWFMM model is simplified and used to analyze complex structures with different modulus in tension and compression. The experimental results of stiffened plate show that the improved GWFMM model can be used to analyze different modulus of tension and compression of complex stiffened structures. In addition, the influence of elastic modulus ratio in tension and compression under different experimental load conditions is further explored, and the influence law of bending and torsion on structures with bi-modulus is discussed. The relevant conclusions provide reference for the design and optimization of full-scale composite structures in marine engineering. [ABSTRACT FROM AUTHOR]

This work studied in detail for the first time the bending of laminated composite plates subjected t mechanical variations by new theory Trigonometric and Trigonometric-Hyperbolic functions of shear deformation. From the Euler-Lagrange hypothesis and the equations of the shear deformation theory, we will develop a present method. One of the most important problems of composite plates is the analysis of their bending behavior. The correct approach used to study their bending behavior includes two trigonometric and trigonometric-hyperbolic functions satisfying the null shear stress condition at the free edges. In this paper the bending problem is solved analytically by developing a computational code and numerically solved by Finite Element Method. In order to simplify the study of the bending behavior, an approach taking into consideration the effect of the transverse shear deformation without the shear coefficient of correction with only four unknowns has been developed while requiring five or more unknowns for other theories. Convergence analysis has been carried and the results are compared to open literature available for plate bending analysis. The approach proves to be simple and useful in analyzing the bending behavior of composite layered plates. [ABSTRACT FROM AUTHOR]

Acoustic metamaterials (AMs) composed of periodic artificial structures have extraordinary sound wave manipulation capabilities compared with traditional acoustic materials, and they have attracted widespread research attention. The sound insulation performance of thin-walled structures commonly used in engineering applications with restricted space, for example, vehicles' body structures, and the latest studies on the sound insulation of thin-walled metamaterial structures, are comprehensively discussed in this paper. First, the definition and math law of sound insulation are introduced, alongside the primary methods of sound insulation testing of specimens. Secondly, the main sound insulation acoustic metamaterial structures are summarized and classified, including membrane-type, plate-type, and smart-material-type sound insulation metamaterials, boundaries, and temperature effects, as well as the sound insulation research on composite structures combined with metamaterial structures. Finally, the research status, challenges, and trends of sound insulation metamaterial structures are summarized. It was found that combining the advantages of metamaterial and various composite panel structures with optimization methods considering lightweight and proper wide frequency band single evaluator has the potential to improve the sound insulation performance of composite metamaterials in the full frequency range. Relative review results provide a comprehensive reference for the sound insulation metamaterial design and application. [ABSTRACT FROM AUTHOR]

Laminated composite plates have become a crucial point of interest in the industry, with the need to ensure sustained and stable structures throughout the plates' lifespan. This study conducted a bibliometric analysis using the Scopus database, gathering 8221 documents for further scrutiny based on the linked meta-data. Utilizing the VOS viewer software version 1.6.19, maps were generated from scientific publishing network data, illustrating connections between researchers' nations and keywords. The investigation into co-occurring phrases associated with laminated composite plates employed author keywords. The results reveal a significant and close relationship among top authors, suggesting a strong research connection, with the United States and China leading the field. Top cited documents and keyword correlations are examined to gauge current research interests. These critical reviews serve as essential resources for scholars and practitioners in the field. Additionally, the review discusses the advancements in and practical applications of different theories for laminated composite plates, with a focus on a bibliometric study using the Scopus database. This paper categorizes models within the context of an equivalent single-layer laminate, analyzing variations in established theories and methodologies for modeling laminated composite plates to offer a nuanced understanding of approaches and assessments in this field. [ABSTRACT FROM AUTHOR]

The composite stiffened plate has garnered significant attention in the lightweight design of ship structures due to its superior mechanical properties. Although it reduces the structural weight, it also increases vibration sensitivity. Thus, investigating the vibration characteristics of the composite stiffened plate is crucial. This paper proposed a theoretical model based on the energy principle and the improved Fourier series method (IFSM) to analyze the composite stiffened plate vibration characteristics. The model demonstrates high reliability and accuracy, as confirmed through convergence analysis and comparison with experimental results from the published literature. Results indicate that geometry and material parameters significantly impact the natural frequency and can mitigate vibration responses by increasing thickness and stiffness. Additionally, ply design parameters markedly influence the vibration of composite stiffened plates, enhancing low-frequency vibration performance through optimal ply design. The structural parameters of the stiffeners, particularly the height and number of stiffeners, play a crucial role, enhancing stiffness and reducing the vibration responses of the composite stiffened plates. [ABSTRACT FROM AUTHOR]

The time difference of arrival (TDOA) method has traditionally proven effective for locating acoustic emission (AE) sources and detecting structural defects. Nevertheless, its applicability is constrained when applied to anisotropic materials, particularly in the context of fiber-reinforced composite structures. In response, this paper introduces a novel COmposite LOcalization using Response Surface (COLORS) algorithm based on a two-step approach for precise AE source localization suitable for laminated composite structures. Leveraging a response surface developed from critical parameters, including AE velocity profiles, attenuation rates, distances, and orientations, the proposed method offers precise AE source predictions. The incorporation of updated velocity data into the algorithm yields superior localization accuracy compared to the conventional TDOA approach relying on the theoretical AE propagation velocity. The mean absolute error (MAE) for COLORS and TDOA were found to be 6.97 mm and 8.69 mm, respectively. Similarly, the root mean square error (RMSE) for COLORS and TODA methods were found to be 9.24 mm and 12.06 mm, respectively, indicating better performance of the COLORS algorithm in the context of source location accuracy. The finding underscores the significance of AE signal attenuation in minimizing AE wave velocity discrepancies and enhancing AE localization precision. The outcome of this investigation represents a substantial advancement in AE localization within laminated composite structures, holding potential implications for improved damage detection and structural health monitoring of composite structures. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study on the dynamic response and impact mitigation capabilities of layered ceramic–polymer–metal (CPM) composites under plate impact loading, focusing on the layer sequence effect. The layered structure, comprising a ceramic for hardness and thermal resistance, a polymer for energy absorption, and a metal for strength and ductility, is analyzed to evaluate its effectiveness in mitigating the impact loading. The simulations employed the VUMAT subroutine of DSGZ material models within Abaqus/Explicit to accurately represent the mechanical behavior of the polymeric materials in the composites. The VUMAT implementation incorporates the explicit time integration scheme and the implicit radial return mapping algorithm. A safe-version Newton–Raphson method is applied for numerically solving the differential equations of the J 2 plastic flow theory. Analysis of the simulation results reveals that specific layer configurations significantly influence wave propagation, leading to variations in energy absorption and stress distribution within the material. Notably, certain layer sequences, such as P-C-M and C-P-M, exhibit enhanced impact mitigation with a superior ability to dissipate and redirect the impact energy. This phenomenon is tied to the interactions between the material properties of the ceramic, polymer, and metal, emphasizing the necessity of precise material characterization and enhanced understanding of the layer sequencing effect for optimizing composite designs for impact mitigation. The integration of empirical data with simulation methods provides a comprehensive framework for optimizing composite designs in high-impact scenarios. In the general fields of materials science and impact engineering, the current research offers some guidance for practical applications, underscoring the need for detailed simulations to capture the high-strain-rate dynamic responses of multilayered composites. [ABSTRACT FROM AUTHOR]

The nonlinear buckling response of laminated composite cylindrical shells reinforced with graphene nanoplatelets (GNPs) is studied in this paper. The functionally graded (FG) shell reinforced by GNPs is analytically studied under external pressure and uniform temperature rise loadings. It is also assumed that the GNP-reinforced laminated composite shell is in contact with an elastic foundation. Various types of profiles are employed for the GNP distribution patterns in the shell thickness including 10 nanocomposite layers. The nonlinear strain-displacement relations of the shallow cylindrical panel are established utilizing the third-order shear deformation shell theory. Governing equilibrium equations of the laminated GNP-reinforced composite shell are formulated employing the principle of virtual displacement. The coupled system of nonlinear differential equations is solved analytically for the hinged–hinged and fixed–fixed boundaries of the shell using a perturbation-based technique. Correctness of presented formulations and obtained solutions is proved by comparisons with results from previous studies for an isotropic cylindrical shell. Novel numerical results reveal that the material properties, geometrical characteristics and load parameters significantly affect on the buckling behavior of laminated composite cylindrical shells. [ABSTRACT FROM AUTHOR]

This paper proposes a simple yet accurate finite element (FE) formulation for the thermomechanical analysis of laminated composites and sandwich plates. To this end, an enhanced first-order shear deformation theory including the transverse normal effect based on the mixed variational theorem (EFSDTM_TN) was employed in the FE implementation. The primary objective of the FE formulation was to systematically interconnect the displacement and transverse stress fields using the mixed variational theorem (MVT). In the MVT, the transverse stress field is derived from the efficient higher-order plate theory including the transverse normal effect (EHOPT_TN), to enhance the solution accuracy, whereas the displacement field is defined by the first-order shear deformation theory including the transverse normal effect (FSDT_TN), to amplify the numerical efficiency. Furthermore, the transverse displacement field is modified by incorporating the components of the external temperature loading, enabling the consideration of the transverse normal strain effect without introducing additional unknown variables. Based on the predefined relationships, the proposed FE formulation can extract the C0-based computational benefits of FSDT_TN, while improving the solution accuracy for thermomechanical analysis. The numerical performance of the proposed FE formulation was demonstrated by comparing the obtained solutions with those available in the literature, including 3-D exact solutions. [ABSTRACT FROM AUTHOR]

Extracting time-varying dynamic characteristics of an aerospace structure under thermal-vibration environment is difficult and complicated since the material properties of the structure fluctuate although the external load is constant. Initially, a composite plate model applied for time-varying system is updated based on finite strip method. Afterward, a thermal-vibration experimental system for realizing high-precision data measurement is designed, and the preliminary experiment certified the validity of experimental method. Finally, the time-varying dynamic characteristics of a typical thermal protective system plate is researched. Results show that the natural frequencies take a downward tendency with respect to heating time, and will undergo a dramatic decrease when the structure reaches the critical bulking temperature, while the damping characteristic shows an adverse trend. In addition, for certifying the applicability and accuracy of the updated model, comparisons between present model and recursive subspace method are conducted. The purpose of this paper is to provide some references on evaluating stability for aerospace structures under severe flight environment. [ABSTRACT FROM AUTHOR]

In this paper, a novel statistical vibration-based damage detection method is developed considering uncertainties in measured resonance frequencies. The proposed method is based on the application of resonance frequencies as the most accurate and easiest measurable vibration feature. For proof of efficiency of the proposed method, case studies were undertaken using two identical composite plates, one delaminated and the other pristine. In this respect, the frequency response functions (FRFs) were measured and used as the main input to the Resonance Detection Algorithm as the proposed method. Applying these FRFs to a Resonance Detector Function can determine the resonant frequencies and their statistical distribution. Through the statistical distributions of the corresponding resonant frequencies, their reliability of detecting damage has been obtained via the beta distribution. By observing the damage detection reliability of the two sets of corresponding resonant frequencies, it has been determined that the changes in natural frequencies are due to structural changes and not random errors through measurement. [ABSTRACT FROM AUTHOR]

This paper presents a study of free and forced vibration of composite sandwich plate with and without damage using the finite element analysis developed under ANSYS APDL software. This modeling uses the 8-node shell 281 element to modelized the composite laminates of the top and bottom face sheets of the sandwich plate and the 20-node higher order solid 186 element to modelized the viscoelastic core. Two sets of boundaries are considered; Simply supported and clamped boundary conditions at all edges. The effect of damaged face sheets layers on natural frequencies, mode shapes, the frequency and transient responses of the sandwich plate is investigated. Numerical results show remarkable shifts of the natural frequencies, frequency and transient responses due to the presence of damage. It is concluded that the natural frequencies decreasing is due to the loss of structural stiffness. Natural frequencies of the sandwich plates are close to those issued from numerical results available in the literature. [ABSTRACT FROM AUTHOR]

Featured Application: The developed new method will allow use for more detailed analysis and characterization of defects that cannot be detected with A0 or S0 modes. Contemporary technologies are employing composite plate materials developed by using various innovative materials (nanostructures, mica structures, etc.). Application of higher-order modes could allow better detection and characterization of defects characteristic of planar plastic and composite structures, mainly due to shorter wavelength. However, excitation of higher-order modes meets many problems, especially in the case of the air-coupled technique, and is not sufficiently investigated. This is relevant in the cases of paper, high-density polyethylene (HDPE), membranes, GFRP, GLARE, CFRP and other composite structures. The objective of the paper was investigation of the excitation and reception of higher-order guided Lamb wave modes in plastic and composite plates. Therefore, it is appropriate to develop new non-contact ultrasonic measurement methods based on the excitation and reception of guided waves for the study of such objects. The obtained results clearly demonstrate the possibility to excite and receive efficiently different higher-order guided Lamb wave modes with very different phase velocities. The presented comparison of the experimental results with the simulation results showed a good agreement. The combination of air-coupled excitation and non-contact reception enables a non-destructive evaluation and characterization of moving plastic objects and composite structures. [ABSTRACT FROM AUTHOR]

Purpose: It is very important to identify the material parameters of composites efficiently and accurately for the dynamic analysis and response prediction of composite structures. In this paper, a high-precision and efficient multi parameter synchronous identification method is proposed for fiber reinforced laminates. Methods: Based on the first-order shear theory and considering the influence of fiber angle, the constitutive model of fiber reinforced laminated composite in any direction is established by using energy method. The model includes four mechanical parameters in a single plane to accurately obtain the anisotropic material parameters. To ensure the accuracy of identification and further accelerate the convergence speed, the Levenberg Marquardt optimization algorithm is innovatively improved, that is, the decision principles of the iterative step and search range are proposed. A detailed parameter identification procedure is proposed, which can identify the four anisotropic parameters once from the modal data of composite plates. Results: Based on experimental tests, the identification method proposed in this paper is used to identify the anisotropic material parameters of laminated composite plates with orthogonal laminated structure and needle structure. Then, the identification process and results of this method are compared with those of the Genetic Algorithm, which verify the accuracy and efficiency of this identification method. Finally, the influences of fiber angle and boundary conditions on the natural frequency are analyzed theoretically. Conclusion: The identification efficiency was doubled that compared with the Genetic Algorithm. The parameter identification method proposed has a good application prospect for other types of composite materials. [ABSTRACT FROM AUTHOR]

Quantitatively and accurately monitoring the damage to composites is critical for estimating the remaining life of structures and determining whether maintenance is essential. This paper proposed an active sensing method for damage localization and quantification in composite plates. The probabilistic imaging algorithm and the statistical method were introduced to reduce the impact of composite anisotropy on the accuracy of damage detection. The matching pursuit decomposition (MPD) algorithm was utilized to extract the precise TOF for damage detection. The damage localization was realized by comprehensively evaluating the damage probability evaluation results of all sensing paths in the monitoring area. Meanwhile, the scattering source was recognized on the elliptical trajectory obtained through the TOF of each sensing path to estimate the damage size. Damage size was characterized by the Gaussian kernel probability density distribution of scattering sources. The algorithm was validated by through-thickness hole damages of various locations and sizes in composite plates. The experimental results demonstrated that the localization and quantification absolute error are within 11 mm and 2.2 mm, respectively, with a sensor spacing of 100 mm. The algorithm proposed in this paper can accurately locate and quantify damage in composite plate-like structures. [ABSTRACT FROM AUTHOR]

Purpose: This work investigates the free vibration response of functionally graded (FG) nanocomposite laminated plates in thermal environments. The nanocomposite plies consist of a polymer matrix strengthened by nano-scale reinforcements, namely a graphene monolayer. This is a case of matrix/graphene mixture or in other words graphene-reinforced nanocomposite (GRNC). Besides the uniform distribution pattern of the graphene reinforcements, four piece-wise FG patterns are also considered to find out the best way to reinforce the nanocomposite plates. The FG distribution patterns are structured by varying the amount of the graphene nano-reinforcements from ply to ply. Methods: Material properties corresponding to the homogenization mixture are carried out using the extended Halpin-Tsai approach. Material properties of the GRNC plies are considered to be either temperature-dependent or temperature-independent. The governing equations of the laminated plate structure are derived based on the first-order shear deformation plate theory (FSDT). The validity of the internal computer program, developed using the finite element method (FEM), is examined by comparing the results obtained in this investigation with those reported in the open literature. Numerical analysis illustrates the effects of a broad range of influencing parameters on the mode shapes and associated natural frequencies of GRNC laminated plates when subjected to varying temperature fields. Results: Numerical results state that the free vibration behavior of the GRNC laminated plates is strongly affected by the variation of the environmental temperature as well as by the geometric parameters. In this context, considering the noteworthy results achieved in this paper, new ideas are proposed to offer innovative insights and novel design models for future real-life applications in polymeric nanocomposite structures. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of an open hole on the stability of a compressed laminated composite plate. The study was carried out in two ways: using experimental tests and numerical analysis. As a result of the experiment, the buckling form and path of the plate were recorded. The form of buckling was determined using the ARAMIS non-contact measurement system. The critical load value was determined from the working path using the approximation method. The experimental results were verified by numerical analysis based on the finite element method. FEM investigations were carried out in terms of a linear eigenproblem analysis. This allowed the bifurcation load and the corresponding buckling form of the numerical model of the plate to be determined. Investigating the effect of the hole in the compressed plate at a critical state showed high agreement between the proposed test methods. No clear effect of the hole size on the buckling of the plate was observed. In contrast, a clear effect of the hole on the critical load value was determined. The maximum decrease in the critical load value was 14%. The same decrease was observed for the stiffness of the post-critical characteristics. It was shown that the [45|−45|90|0]s composite plate had more than three times lower strength compared to [0|−45|45|90]s and [0|90|0|90]s. The novelty of this article is the development of a research methodology based on new interdisciplinary research methods for describing the influence of the central hole on the stability of compressed composite plates. The ABAQUS system was used for the numerical analysis. [ABSTRACT FROM AUTHOR]

In this paper, a research on theoretical analysis and finite element simulation of the damping sandwich composite plate with fixed support condition is carried out, and the dynamic characteristics of composite plates are explored by modal experiments. The vibration equilibrium equation of damping sandwich composite plate with fixed support condition is derived by combining first-order shear deformation theory, variational principle, and Hamilton principle. A set of modal basis functions satisfying the fixed support condition are established. The analytical solution is obtained via Galerkin weighted residual theory. The influence of structural parameters on the free vibration characteristics of the sandwich composite plates is investigated based on the mutual verification of theoretical calculation, numerical simulation, and modal test results. When the damping layer (0.2 mm) is located on the surface of the skin (2 mm), the first-order mode frequency and first-order loss factor are 196.66 Hz and 0.01, respectively. When the damping layer is in the neutral layer, the first-order mode frequency and first-order loss factor are 189.99 Hz and 0.14, respectively. Compared with the damping layer in the skin, the first-order mode frequency is reduced by 3.39%, while the first-order loss factor is 14 times higher. The results show that the damping performance of the structure is optimal when the damping layer is located in the neutral layer, and the structural stiffness is higher when the damping layer is close to the skin. The work provides theoretical guidance for the development and application of lightweight composite structures with large damping and high stiffness. [ABSTRACT FROM AUTHOR]

This manuscript concerns the investigation of the influence of the open hole on stability of the compression plate made of carbon-epoxy composite. Experimental tests carried out on the real plate resulted in a postcritical path from which the critical load value was determined using appropriate approximation method. In parallel, an independent study was carried out based on a numerical analysis using the finite element method (FEM). Investigations were conducted in terms of a linear eigenproblem analysis, from which the value of the bifurcation load was determined for the FEM model of the plate. Its values resulting from the numerical analyses were validated against the experimental results, thus confirming the adequacy of the designed FEM model of the plate. The paper shows that the incremental increase of the hole in the plate monotonically influences the decrease in the critical load of the plate. The largest decrease was observed for the specimen with the largest hole analysed and was 13.5% compared to a plate without a hole. The newness of the paper is the application of interdisciplinary investigation methods to describe the influence of the open hole compression (OHC) on the stability of composite plates. ABAQUS® was used as the tool with which the numerical analyses were realised. [ABSTRACT FROM AUTHOR]

This paper researches the free vibrations and corresponding material parameters of a functional gradient graphene platelets-reinforced composite (FG-GPLRC) cantilever torsional plates with both pore and graphene variations in the transverse direction. Utilizing the feature of closed-cell cellular solids, the mixture rule, and the modified Halpin–Tsai model, the material parameters of the composite are determined for different volume fractions of component materials. Then, using the classical plate theory (CLPT), the Rayleigh–Ritz technique and polynomials, the dynamic equation that can be used to obtain the free vibration mode shapes and frequencies of the rotating cantilever torsional plate is given. Comparison studies with the previous calculation results from available literature and the finite element (FE) models of cantilever plates are conducted, and the correctness of the present theoretical formulation and numerical calculation is verified. Finally, the effects of graphene platelet (GPL) distribution, porosity distribution (PD), GPL content, rotational speed, and average geometric size of GPL on free vibrations of the system are studied in depth. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the preparation of AlN and Al2O3, as well as the effect of nano-AlN and nano-Al2O3, on friction and wear properties of copper-steel clad plate immersed in the lubricants. Design/methodology/approach: Nano-AlN or nano-Al2O3 (0.1, 0.2, 0.3, 0.4 and 0.5 Wt.%) functional fluids were prepared. Their tribological properties were tested by an MRS-10A four-ball friction tester and a ball-on-plate configuration, and scanning electron microscope observed the worn surface of the plate. Findings: An increase in nano-AlN and Al2O3 content enhances the extreme pressure and anti-wear performance of the lubricant. The best performance is achieved at 0.5 Wt.% of nano-AlN and 0.3 Wt.% of nano-Al2O3 with PB of 834 N and 883 N, a coefficient of friction (COF) of approximately 0.07 and 0.06, respectively. Furthermore, the inclusion of nano-AlN and nano-Al2O3 particles in the lubricant enhances its extreme pressure performance and reduces wear, leading to decreased wear spot depth. The lubricating effect of the nano-Al2O3 lubricant on the surface of the copper-steel composite plate is slightly superior to that of the nano-AlN lubricant, with a COF reaching 0.07. Both lubricants effectively fill and lubricate the holes on the surface of the copper-steel composite plate. Originality/value: AlN and Al2O3 as water-based lubricants have excellent lubrication performance and can reduce the COF. It can provide some reference for the practical application of nano-water-based lubricants. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0255/ [ABSTRACT FROM AUTHOR]

Purpose: In this paper, the free vibration and dynamic response of laminated composite wave plate in a thermal environment are investigated by means of the mesh-free strong form method. Method: The wave plate is divided into several rectangular and cylindrical segments, and each segment is transformed into a square domain or equivalent cylindrical rectangular domain through a coordinate mapping technique to ensure numerical stability. The theoretical formulation of the individual segment is established using Hamilton's principle in the framework of first-order shear deformation theory (FSDT), and the thermal effects on the wave plate are considered by employing the thermo-elastic theory. The discretized equations are obtained directly from the strong forms of governing equations in which displacement components are approximated by a mes-hfree Tchebychev-radial point interpolation method (TRPIM) shape function. The formulation of the entire wave plate is obtained using coupling conditions between the segments. The harmonic distributed load and stationary/nonstationary stochastic excitation are considered as the external force. Results: Convergence and verification studies are performed to confirm the reliability and accuracy of the present formulation. Satisfactory agreements are achieved between the numerical results of the proposed method and those from the published literature. Finally, the effect of some parameters on the free vibration and dynamic response of laminated composite wave plate is presented. [ABSTRACT FROM AUTHOR]

To operate small and medium-sized helicopters even under critical icing conditions, new deicing technologies are necessary because the existing heating solutions cannot be economically downscaled without drastically reducing the helicopters' payload. Therefore, this paper investigates the potential of a low-frequency electromechanical deicing (EMDI) system for an actual fiber composite helicopter structure and its combination with an ice detection system that uses the EMDI components for ice detection. The primary objective of this study is the design of the deicing system for a given helicopter structure and its evaluation under realistic icing conditions. Experimental and numerical modal analyses are used to analyze the vibration behavior of the structure and to select favorable positions and phase relations for the actuators. To determine the performance of the EMDI system, experimental deicing tests were performed in a deicing test facility that is able to generate realistic icing conditions. The EMDI system can cause delaminations and cracks in glaze ice layers and partially remove the ice on the test object. The results show that there is an upper and lower limit for ice thickness at which the system is effective. Therefore, the system needs to be combined with an ice detection system that is capable of measuring the ice thickness on the surface of the structure. Using the piezoelectric actuators of the EMDI, this can be achieved by monitoring their impedance changes, which is experimentally proven for different ice thicknesses and different temperatures on a carbon fiber composite plate. The findings of this study support the idea of a combined ice detection and deicing system using the same hardware components. Integrating an autonomous control system, local icing phenomena on a rotorcraft structure can be detected and consequently, ice accretion can be removed with low energy consumption. [ABSTRACT FROM AUTHOR]

Purpose: The main purpose of this paper is to detect the damage of interior delamination in composite laminate using a new non-destructive testing method of highly nonlinear solitary waves. We studied the coupling mechanism between highly nonlinear solitary waves and interior delamination composite plate. Methods: The discrete element method is used for the one-dimensional particle chain, based on the residual stiffness model, Hertz's contact law and the composite plate vibration differential equation are used, we obtained the coupled differential equations for one-dimensional particle chain and interior delamination composite plate. We used the fourth-order Runge–Kutta method to solve the differential equations, and obtained the velocity curve and displacement curve of each particle in the particle chain. The influence of the thickness of the damaged composite plate, the average diameter of the interlaminar cracks, and the density of the interlaminar cracks on the reflected solitary waves are analyzed. We used one-dimensional homogeneous particle chain and one-dimensional composite particle chain to detect damaged composite plate with different material properties. Results: The results shows that the reflected waves are sensitive to the thickness of the plate, the average diameter of the interlaminar cracks and the density of the interlaminar cracks. We find that the propagation time of solitary waves in the composite particle chain is shorter and faster, and the detection efficiency can be increased by 23.5% at most. Conclusions: The characteristic information carried by reflected waves can be used for non-destructive testing of damaged composite plate. The research results of this paper enrich and improve the non-destructive testing of composite materials, and accelerate the practical application of one-dimensional particle chain. [ABSTRACT FROM AUTHOR]

In this paper, the low-velocity impact response of composite plates in the presence of pre-loads is investigated using three new models for contact force estimation. The boundary conditions are considered as simply supported and the behavior of the material is linear elastic. The equations are based on both classical and first order shear deformation theory and the Fourier series method is used to solve the governing equations. The mass of the impactor is considered to be large mass and therefore the impact response is categorized as quasi-static. In the first impact model, the contact force history is first considered as a half-sine and then the maximum contact force and contact duration are calculated. In the second model, an improved two degree of freedom (ITDOF) spring-mass system is expressed by calculating the effective contact stiffness using a fast-iterative scheme. In the third model, which is expressed for the first time in this paper, the plate is considered as a series of masses and springs constructing a multi degree of freedom (MDOF) spring-mass system and the average forces applied to springs is introduced as the contact force. Validation of these models is done by comparing the results with the analytical, numerical and experimental results and shows good agreement. Results show that the new MDOF spring-mass system is more accurate for calculating the contact force rather than the ITDOF spring-mass system. [ABSTRACT FROM AUTHOR]

In this paper, low-velocity impact resistance for composite laminates is introduced. The resistance function for the parameters of low-velocity impact performs 2-order Taylor's series expansion. The orthogonal design and Latin hypercube design are presented and their strongpoint and shortcoming are also indicated. The low-velocity impact simulation model of the composite plate is established. The computed results are compared with the existing standard test from ASTM D7136M-05 and the simulation parameters of the model are modified. By calculating and analyzing typical honeycomb sandwich models with different configurations, the damage-area resistance is extracted from the results. The discrete and abstract variables are treated as continuous integer variables to fit the resistance formula of the composite material. Response surface approximation is used to form a hyper surface formula for parameters. The sensitivity analysis of it reveals that the two most influential factors, related to the resistance definition, which is convenient for the subsequent structural design of the composites. In contrast to the previously defined Taylor's series expansion, the initial coefficients of the resistance formula are obtained. The resistance hyper surface function obtained from the simulation data is used to design the 7-point low-speed impact tests using Latin hypercube design, which employed to verify and validate the simulations, for purposes of saving on the cost of testing and improving the accuracy of analysis. [ABSTRACT FROM AUTHOR]

In this paper, the influence of design parameters on the strength of steel–concrete composite shear walls is investigated by means of finite element (FE) simulations. The shear wall typology studied in this paper consists of multiple composite plate shear wall-concrete encased on one or both sides of the plates. The FE models include contact technology to capture debonding between concrete and steel, tensile cracking in concrete, and large deflection theory involving local instabilities. Some design parameters considered in this work are the height-to-width ratio of the steel plates and their thickness, number of steel plates, the cross-section of the columns, and the height-to-width ratio of the shear wall. Furthermore, a sensitivity analysis of the normalised shear strength per unit cost of structure for these design parameters is also studied. Our numerical predictions are validated successfully with experimental data reported in the literature, revealing the predictive capabilities of the model. The present results provide further insight into the structural behavior of steel–concrete composite shear walls and pave the way for the future development of more efficient and innovative steel–concrete composite systems. [ABSTRACT FROM AUTHOR]

Automatic defect-detection technology based on deep learning is increasingly used for distinguishing production quality by many industries. However, production lines are usually installed with lots of function modules, which make it difficult to integrate new modules. Common deep learning models run on PC platforms and require a big space with high cost, while ARM64 mobile platforms are much smaller with less cost and equivalent connectivity but also weaker performance. Considering these facts, ARM64 platforms with a fully optimized model are the best solution for adding a defect-detection function for existing production lines. This paper focused on a mobile-optimized model to achieve higher speed and equivalent precision on the ARM64 mobile platform for detection. First, the model structure is simplified by reducing the redundancy of feature maps to increase the network inference speed. Second, a convolutional block attention module is attached to compensate for the decrease in precision caused by structure simplification. Furthermore, a transfer learning method is adopted to improve training performance. Finally, the trained and compiled module is exported to the PyTorch Mobile format and deployed on the mobile platform application to execute its defect-detection function. The results show that the optimized network achieves a speed of 2.124 fps, 210.7% compared with that of You Only Look Once v5n, i.e., 1.008 fps, on the RK3399 ARM64 platform, and has an average mAP of 99.2%. The studied mobile-optimized model has better speed and equivalent precision and can be available on many different ARM64 platforms regardless of the processor manufacturer. It can satisfy the need for real-time defect detection and can be used in similar scenarios. In the future, more improvements could be made such as deploying on platforms with NPU support to achieve faster speed, exploring the relationships between dataset properties and transfer learning effects, even training and running the model directly on ARM64 platforms. [ABSTRACT FROM AUTHOR]

The R&D Building of Zhanjiang Bay Laboratory is a high-rise structure with multiple irregular items exceeding the specification limit, employing a steel frame-shear wall structural system. The outer frame consists of square steel tube concrete columns and solid-web steel beams, while the core shear wall uses a double steel plate concrete composite shear wall. This paper employs the architectural structural calculation software YJK-EP to perform a dynamic elastic-plastic time-history analysis under rare earthquake action. The shear and bending resistance of the shear wall at the maximum shear force and bending moment are checked to meet the requirements of the "Technical Specifications for Concrete Structures of High-rise Buildings". The maximum inter-story displacement angle meets the requirements of the "Code for Seismic Design of Buildings". The double steel plate concrete composite shear wall Wall-1, connected to a large-span and heavy-load transfer truss, was verified under significant seismic action using the ABAQUS software. The results indicate that Wall-1 can meet the design target requirements under major earthquake conditions. Finally, a dynamic nonlinear analysis method was employed using MIDAS-GEN software to study the structure's anti-progressive collapse performance. The results show that under seven different scenarios, the maximum rotational angle of the remaining structural horizontal members is 2.02°, far less than the limit set by GSA, indicating that a progressive collapse did not occur. In the scenario where the corner column is removed, both the maximum shear and bending moment values for Wall-1 are far below its shear and bending resistance capacities, satisfying the load-bearing requirements. The removal of the corner column has a significant impact on the displacement of the columns on the same level nearby, with the peak displacement change rate reaching 702.65%. [ABSTRACT FROM AUTHOR]

Smart laminated composite structures with piezoelectric patches are widely used in vibration control applications in several engineering fields. Precise mathematical models are required for the coupling of base structural and piezoelectric field variables. This paper presents the electro-structural analysis and optimization studies of piezoelectric energy harvester with laminated composite substrate plate subjected to base excitations. The coupled electro-mechanical equations are derived from recently proposed first-order shear deformation theory via the Hamilton's principle by considering hygrothermal effects. The coupled-field solution is obtained from Ritz-approximation and validated with three-dimensional finite element analysis. Effects of multiple piezoelectric patch topologies over the plate surface on the open-circuit voltage and displacement response are illustrated. Furthermore, the influences of piezoelectric-patch sizes, ply-orientation, size, and location of the tip mass are initially studied on the magnitude of output power and efficiency. An optimization study is conducted to identify the geometric and material variables for improvement of the harvester power output and efficiency. [ABSTRACT FROM AUTHOR]